public String addMembershipListener(MembershipListener listener) {
if(listener == null){
throw new NullPointerException("listener can't be null");
}
EventService eventService = nodeEngine.getEventService();
EventRegistration registration;
if (listener instanceof InitialMembershipListener) {
lock.lock();
try {
((InitialMembershipListener) listener).init(new InitialMembershipEvent(getClusterProxy(), getMembers()));
registration = eventService.registerLocalListener(SERVICE_NAME, SERVICE_NAME, listener);
} finally {
lock.unlock();
}
} else {
registration = eventService.registerLocalListener(SERVICE_NAME, SERVICE_NAME, listener);
}
return registration.getId();
}